Noob question: Should/Can a path be deleted after the agent has reached it’s destination? Or does this happen automatically?
As long as all references to it are gone, it will be collected by the garbage collector.
If you really want to optimize memory usage, you can use path pooling. But this is only if you have identified the GC as a bottleneck. See http://arongranberg.com/astar/docs/pooling.php